Noise measuring SFC1000 with Jota cans.

redfox

redfox

Hero member
To be a little up front on things, because of stricter local rules regarding noise, I've been to a MOT station today with the SFC1000, which runs 36mm downpipes and two original Jota end cans. Result was 81,4 db (A) measured according to the official method and calibration etc, which is well within the laws limit of 84db +3db for being a used motorcycle. So far so good.

Kind regards,
Jacques
 
  • Like
Reactions: AJR
redfox said:
To be a little up front on things, because of stricter local rules regarding noise, I've been to a MOT station today with the SFC1000, which runs 36mm downpipes and two original Jota end cans. Result was 81,4 db (A) measured according to the official method and calibration etc, which is well within the laws limit of 84db +3db for being a used motorcycle. So far so good.

Kind regards,
Jacques
Click to expand...
81 dB at 4500 revs?
 
MOT testing station with a DB measuring device??
new one on me is that, or are we talking non UK?
CLEM
 
Different regulations apply in different countries. In ours, there are 5 or 6 different methods how to measure the noise, depending of the age of the bike (first registration date counts...). For my Jota f.e., that would mean that with the modern method (0,5 meters behind the exhaust outlet in 45° angle at 1/2 of the 8.900 revs shown in the paper for maximum power), they would have to add 21dB to cover the different measuring methodes and 5dB for the fact that exhausts get louder under usage. My papers show 84dB for idle noise, which means with the current method, it could do 84 + 5 + 26 = 115dB...

A bit different for the 1000 SFC though...
 
Lothar,
I've seen the German reg for the 21dB added to the measurement result if the bike was first registered before 1980, but where did you get the information that 5 dB are added for older exhausts? As you know all to well many have had to go through lenghty and costly court ordeals to get their impounded bikes back, even when proven to be within the legal noise limits.
 
There's no noise limit in France on motorcycles before spring 1976.

81 dB still sounds very low, near the sound produced by tyres and chain as the bike goes by with the engine not running, so I've read.

Paul
 
Recently got MOT in UK on my 88 SFC1000 with SS Jota style silencers. No measurements were taken. At tickover it's quite sensible. it's only when you give it big revs does it attract attention. Must be a mean spirited tester somewhere?
 
Gerald said:
Lothar,
I've seen the German reg for the 21dB added to the measurement result if the bike was first registered before 1980, but where did you get the information that 5 dB are added for older exhausts? As you know all to well many have had to go through lenghty and costly court ordeals to get their impounded bikes back, even when proven to be within the legal noise limits.
Click to expand...

Page 10, Point 2.3 ;-)

I have also checked this with Mr. Rütter from TÜV Rheinland. The 5 dB are only for exhausts that are already in the papers, not for those that you want to get into the papers (even if they are used at the time of the registration). The 5dB are therefore for the road-test (Police) or the TÜV if they have doubts about the exhaust being legal.

here the original post some years ago in the german forum: https://www.laverda-register.de/forum/phpBB3/viewtopic.php?p=847&hilit=messverfahren#p847
 
Last edited:
Laverdalothar said:
Different regulations apply in different countries. In ours, there are 5 or 6 different methods how to measure the noise, depending of the age of the bike (first registration date counts...). For my Jota f.e., that would mean that with the modern method (0,5 meters behind the exhaust outlet in 45° angle at 1/2 of the 8.900 revs shown in the paper for maximum power), they would have to add 21dB to cover the different measuring methodes and 5dB for the fact that exhausts get louder under usage. My papers show 84dB for idle noise, which means with the current method, it could do 84 + 5 + 26 = 115dB...
Click to expand...

WTF? That doesn't make sense to me. Adding 21dB to cover different measuring methods sounds like a crock of shit. Why don't they simply standardise their measuring method? If you do a sound level test with non-controlled method, then the reading you get is pretty much a random number. Simply adding 21 to it doesn't make it any less random. It certainly doesn't make it correct.

Besides, you can't simply add dB. Decibels are a logarithmic unit so summing them arithmetically is meaningless. For example, the arithmetic sum of 84dB + 21dB is 105dB, but the logarithmic sum is 97.2dB.

I think there are too many people making up rules about noise who have no clue about accoustics.
 
Thanks Lothar, I'll bookmark the link on my cell phone in case I get stopped and checked.

@Cam, you'll find a lot of nonsense in German regulations and a lot of pseudo intellectuals trying wreak havoc on the nation.
 
Dellortoman said:
WTF? That doesn't make sense to me. Adding 21dB to cover different measuring methods sounds like a crock of shit. Why don't they simply standardise their measuring method? If you do a sound level test with non-controlled method, then the reading you get is pretty much a random number. Simply adding 21 to it doesn't make it any less random. It certainly doesn't make it correct.

Besides, you can't simply add dB. Decibels are a logarithmic unit so summing them arithmetically is meaningless. For example, the arithmetic sum of 84dB + 21dB is 105dB, but the logarithmic sum is 97.2dB.

I think there are too many people making up rules about noise who have no clue about accoustics.
Click to expand...
Hi Cam, They can't do the old measuring method, as you can not find a place aside of the road where this method is legal (no buildings, no other vehicles, no walls, bushes etc. around in a distance of 25 meters at least around the bike and the measuring device; even a passing car compromises the result). The other method is a bit more "practical" as the distance to these barriers/obstacles may be 3 meters. Also, it is an easy way of removing the discussion about the measuring method and standardize it for all bikes. The old ones like ours are not the problem the police wants to get control of. It is the modern bikes with the removed dB-eaters. I ran my Jota for roughly 2-3 years with a megaphone exhaust (the factory 3-1 with no muffling at all). I NEVER was stoped and noise testet. Mostly because I did not rev the bike to the limits but - especially in towns - shifted up to the highest gear possible and just rolled around (with some exceptions, which were in areas with no houses etc.)

I am glad they have to add these 21dB, otherwise Slaters "Jota-cans" would be absolutely illegal to ride (well - they are actually non the less, but at least you stay within the legal results when police measures them...). I have tried to calm down the jota cans even with dB-eaters, but that killed so much power that I removed them again.
 
I think I may have misunderstood your earlier post Lothar. I thought they were adding 21dB to your bike's sound level reading. Not subtracting it, which would make a whole lot more sense.
 
You Europeans have some strange rules. Here in California, motorcycles are never inspected ever. Although we have rules on how much noise your bike can make, they are never enforced. As for safety aspects, such as your tires are worn out and your brakes and lights don't work, no one cares. You can modify the bike any way you want.

Cars in some areas of California need an inspection for emissions testing, but that is it. Most other states don't test for this either.

We commonly see vehicles that are barely able to move down the road do to numerous problems but that is OK to.
 
I got nailed in California early one morning riding up to Skyline Boulevard on the SFC with open 2/1, also a mate with a Velo with the original fishtail muffler. CHP had been listening to us come up the hill for quite a while. IIRC I got a fine and fix it ticket. Ignored both as I left California some months later.
 
When I moved interstate to South Aus the RGS had to 'go over the pits' to change over to SA rego.
The bike is fitted with 'Staintune' mufflers which are a bit louder than standard.
The exhaust volume was measured with a microphone mounted at about a 75 cm above the ground placed at 45 degrees to the pipe at around 1.5 metres distant. The book said that the bike had to be measured at 5000 rpm and not to be greater than 86 db, the bike came in at 83 which was well within the limit.
 
IOM rules are AFAIK 97db for ‘modern’ bikes but you can probably get away with around 100db. Older Bikes that pre date the EU changes around 1982, which killed off the Montjuic, are allowed whatever was fitted at date of manufacture.
 
Dellortoman said:
I think I may have misunderstood your earlier post Lothar. I thought they were adding 21dB to your bike's sound level reading. Not subtracting it, which would make a whole lot more sense.
Click to expand...
Hi Cam,

what they do is: if your papers of the bike show f.e. 84dB, they need to add to this value in the paper a tolerance of 5dB for used exhausts. If they measure the bike below 89dB, everything is OK.

For older bikes, they have to add another 21dB to the value in the papers plus the tolerance for compensating the different measuring method, which brings you to 84 + 5 + 21 => 110dB. Everything they measure below 110 dB in this case has to be accepted as legal.
 
1200ts said:
You Europeans have some strange rules. Here in California, motorcycles are never inspected ever. Although we have rules on how much noise your bike can make, they are never enforced. As for safety aspects, such as your tires are worn out and your brakes and lights don't work, no one cares. You can modify the bike any way you want.

Cars in some areas of California need an inspection for emissions testing, but that is it. Most other states don't test for this either.

We commonly see vehicles that are barely able to move down the road do to numerous problems but that is OK to.
Click to expand...
well - it might be no one enforces them, but you have noise regulations, too...:


regarding there is no inspection and you can do to your bike what you want - maybe that is why 3-4 times more people (or twice as many Motorbikers) are killed in USA /100.000 citizens than in Germany...

en.wikipedia.org

List of countries by traffic-related death rate - Wikipedia

en.wikipedia.org en.wikipedia.org
 
You must log in or register to reply here.
Back
Top